Updated

A man convicted of breaking into his neighbor's home in a St. Louis suburb and slitting her throat 25 years ago was executed early Wednesday.

Walter Timothy Storey was the first Missouri inmate put to death this year after a record 10 executions in 2014. His fate was sealed when the U.S. Supreme Court refused to halt the execution over concerns about Missouri's secretive process for obtaining and using the lethal injection drug pentobarbital.

Strapped to the gurney, Storey mouthed what appeared to be "I love you" to his witnesses and the family of the victim, Jill Frey.

He appeared to then start singing or chanting — it was impossible to tell because of the thick glass separating the execution room from the viewing area. Seconds after the drug was administered at 12:01 a.m., he stopped suddenly and heaved one deep final breath. He was pronounced dead at 12:10.

Storey was sentenced to death three separate times in the same case. He was living with his mother in a St. Charles apartment on Feb. 2, 1990, when he became upset over his pending divorce. He spent an angry night drinking beer.

He ran out of beer and money, so he decided to break into the neighboring apartment of Frey to steal money for more beer.

Frey, a 36-year-old special education teacher, had left the sliding glass door of her balcony open. Storey climbed the balcony and confronted Frey in her bedroom, where he beat her. Frey suffered six broken ribs and severe wounds to her head and face.

Storey used a kitchen knife to slit her throat so deeply that her spine was damaged. Frey died of blood loss and asphyxiation.

Storey left the body and returned the next day to clean up blood, throw clothes in a trash bin and scrub Frey's fingernails to remove any traces of his skin.

But he missed a key piece of evidence: blood on a dresser.

"There was a really good palm print in blood," said Mike Harvey, a retired St. Charles detective who now works as an investigator for the St. Charles County prosecutor.

Lab analysis matched the print to Storey, whose prints were on file for a previous crime.

Storey was convicted and sentenced to death.

The Missouri Supreme Court tossed the conviction, citing concerns about ineffective assistance of counsel and "egregious" errors committed by Kenny Hulshof, who was with the Missouri attorney general's office at the time and handled the prosecution. Hulshof was later a congressman and a candidate for governor.

Storey was tried again in 1997, and sentenced again to death. That conviction was also overturned, this time over a procedural error by the judge. Storey was sentenced to death a third time in 1999.

Storey's attorney, Jennifer Herndon, said he spent "thousands of hours" working in a restorative justice program in prison, trying to help crime victims. She said he was remorseful for the killing.